Cron job troubles

[Marcus Lam]

I've added a job to the task scheduler under my domain. It was supposed to call a php script located in my web server. After the cron job was called, I received an email saying "Permission denied". I figured it was because the user I have assigned the job under didn't have enough permission. So, I returned to the Plesk control panel. This time, instead of going to domains, I went to server > scheduled tasks. I selected adm as the system user. Under preferences, I typed in the same mail address as before. I've then added the same cron job to the scheduler. However, this time, even after the appointed time has passed, I did not receive an email reporting the cron job's result. I tried going back to posting a task under the domain name from earlier. Now that ceased to work as well. I no longer receive any emails, no matter where I'm assigning the cron job from.

I'm new to this, and I would really appreciate some advice. If I'm not receiving any emails, how can I clarify what the issue is? I tried looking under the error logs, but I didn't see anything related to the cron jobs I've added. Thank you. Please let me know if you need more information.